1. Field of the Invention
This invention relates to binding assays, particularly immunoassays, using a detection system with more than one detectable substance.
2. Brief Description of the Prior Art
Problems confronting the art of immunoassays have included the difficulty of simultaneous detection of more than one analyte, a need for detectable labels to measure analytes, a need for good visual determination of label with or without instrumentation, a need for discrimination of signal above noise if instrumentation is used and a need for increased sensitivity.
To increase sensitivity and allow visual detection in assays, analytes, that is, antibodies, antigens or haptens, have been labeled with dyes or fluorochromes. For example, U.S. Pat. No. 4,695,554 describes sacs or liposomes containing a single dye for use in immunoassays.
U.S. Pat. No. 4,703,017, the entire disclosure of which is herein incorporated by reference, describes a solid phase assay using a single colored particulate label such as a liposome including a dye.
U.S. Pat. No. 4,745,075 describes agglutination assays using two or more insoluble colored particles such as non-viable bacterial cells, alginate particles, sepharose beads, silica, alumina, erythrocytes and polymer latexes. The particles are adapted to form different colored agglutinates depending on the presence of specific ligands.
As is known by the skilled artisan, agglutination assays, e.g. the Weil-Felix Test, the Latex Particle Test, agglutinations mediated by lectins or by fibrinogen, etc., do not use solid supports. Agglutination assays use visual and microscopic detection of aggregates which are suspended or aggregated.
There is need for a more sensitive assay than one which relies on a single colored particulate label or color related agglutination. A technique for the enhancement of signal has now been discovered through the use of multi-colored particulate labels in an assay which utilizes a solid support.